java反射实例

java反射实例：

import java.lang.reflect.*;
import java.util.*;
  
   public class GenericReflectionTest
   {
      public static void main(String[] args)
      {
         // read class name from command-line args or user input
         String name;
        if (args.length > 0)
           name = args[0];
        else
        {
           Scanner in = new Scanner(System.in);
           System.out.println("Enter class name (e.g. java.util.Date): ");
           name = in.next();
        }
 
        try
        {
           // print generic info for class and public methods
           Class cl = Class.forName(name);
           printClass(cl);
           for (Method m : cl.getDeclaredMethods())
              printMethod(m);
           	  printFiles(cl);
        }
        catch (ClassNotFoundException e)
        {
           e.printStackTrace();
        }
     }
 
     private static void printFiles(Class cl) {
		// TODO Auto-generated method stub
		Field[] files=cl.getDeclaredFields();
		for (Field field : files) {
			field.setAccessible(true);
			System.out.print(Modifier.toString(field.getModifiers())+ "   ");
			printType(field.getGenericType());
			System.out.print("   "+field.getName()+" \n");
		}
	}

	public static void printClass(Class cl)
     {
        System.out.print(cl);
        printTypes(cl.getTypeParameters(), "<", ", ", ">");
        Type sc = cl.getGenericSuperclass();
        if (sc != null)
        {
           System.out.print(" extends ");
           printType(sc);
        }
        printTypes(cl.getGenericInterfaces(), " implements ", ", ", "");
        System.out.println();
     }
 
     public static void printMethod(Method m)
     {
        String name = m.getName();
        System.out.print(Modifier.toString(m.getModifiers()));
        System.out.print(" ");
        printTypes(m.getTypeParameters(), "<", ", ", "> ");
 
        printType(m.getGenericReturnType());
        System.out.print(" ");
        System.out.print(name);
        System.out.print("(");
        printTypes(m.getGenericParameterTypes(), "", ", ", "");
        System.out.println(")");
     }
 
     public static void printTypes(Type[] types, String pre, String sep,  String suf)
     {
        if (types.length > 0) System.out.print(pre);
        for (int i = 0; i < types.length; i++)
        {
           if (i > 0) System.out.print(sep);
           printType(types[i]);
        }
        if (types.length > 0) System.out.print(suf);
     }
 
     public static void printType(Type type)
     {
        if (type instanceof Class)
        {
           Class t = (Class) type;
          System.out.print(t.getName());
        }//下面的是泛型类型
        else if (type instanceof TypeVariable)
        {
           TypeVariable t = (TypeVariable) type;
           System.out.print(t.getName());
           printTypes(t.getBounds(), " extends ", " & ", "");
        }
        else if (type instanceof WildcardType)
        {
           WildcardType t = (WildcardType) type;
           System.out.print("?");
           printTypes(t.getLowerBounds(), " extends ", " & ", "");
           printTypes(t.getUpperBounds(), " super ", " & ", "");
        }
        else if (type instanceof ParameterizedType)
        {
           ParameterizedType t = (ParameterizedType) type;
           Type owner = t.getOwnerType();
           if (owner != null) { printType(owner); System.out.print("."); }
           printType(t.getRawType());
           printTypes(t.getActualTypeArguments(), "<", ", ", ">");
       }
       else if (type instanceof GenericArrayType)
       {
          GenericArrayType t = (GenericArrayType) type;
          System.out.print("");
          printType(t.getGenericComponentType());
          System.out.print("[]");
       }

    }
 }